A spokesman for the embassy denied on Thursday that a safe, the handling of which triggered the explosion, had not been opened for two decades.

"The safe was used on a daily basis. The money for the employees was kept there. It was a mechanical safe, purchased in Vienna," said Nabil al-Fahel.

His statement came after Riyad al-Malki, the Palestinian foreign minister, was quoted as saying that the safe was not opened for two decades and that it was unknown what it contained.

Fahil also denied the possibility that the object was "secured with explosives" - something that would be illegal in the Czech Republic, and that would mean the Palestinian diplomatic mission had violated international conventions.

Czech police chief Martin Červiček said that the authorities would seek an explanation from the Palestinians about the safe being secured with explosives to prevent unauthorized access.

The Czech police on Wednesday ruled out the possibility that the accident was a terrorist attack. However, an unnamed Palestinian official was quoted by the New China news agency as saying that "it could have been an assassination."

The embassy spokesman also did not rule out the possibility that the ambassador was attacked, and said that since the safe was not secured using explosives, it was unknown how they got there.

Czech police spokeswoman Andrea Zoulova said last night that the investigation had shown that the system securing the safe exploded due to mishandling, while other circumstances were still unknown, considering that the main witness died.